Cobalt salophen complexes for light-driven water oxidation

Md Ali Asraf, Hussein A. Younus, Chizoba I. Ezugwu, Akshay Mehta, Francis Walter Cornelius Verpoort

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Earth-abundant molecular complexes have been found to be excellent catalysts for the light-driven water oxidation reaction. Here, we demonstrate the photochemical water oxidation catalysed by three cobalt salophen complexes with different axial ligands in the presence of [Ru(bpy)3]2+ as a photosensitizer and Na2S2O8 as an electron acceptor in phosphate buffer of pH 9 and 7. The electrochemical investigation of the complexes in pH 9 including cyclic voltammetry (CV) and linear sweep voltammetry (LSV) verify the deposition of catalytic films on the surface of the working electrode. The deposited film characterization using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) confirms that the complexes decomposed to form nanoparticles. Electrospray ionization mass spectrometry (ESI-MS) studies along with dynamic light-scattering (DLS) measurements of the catalyst solution during the course of photochemical water oxidation suggest the catalyst decomposition and the formation of nanoparticles. The XPS measurements of the produced nanoparticles suggest that the surface of the particles is composed of Co(ii) and OH species. In contrast, multiple experiments argue that light-driven water oxidation using the same complexes in pH 7 is homogeneous. We thus conclude that cobalt salophen complexes act as precatalysts that decompose under basic conditions to form cobalt hydroxide nanoparticles which act as a real catalyst for the light-driven water oxidation reaction, whereas the same complexes act as a homogeneous catalyst in the photochemical water oxidation reaction under neutral conditions.

Original languageEnglish
Pages (from-to)4271-4282
Number of pages12
JournalCatalysis Science and Technology
Volume6
Issue number12
DOIs
Publication statusPublished - 2016
Externally publishedYes

Fingerprint

Cobalt
Oxidation
Water
Catalysts
Nanoparticles
Electrospray ionization
Photosensitizing Agents
Photosensitizers
Dynamic light scattering
Voltammetry
Cyclic voltammetry
Mass spectrometry
salophen
Energy dispersive spectroscopy
Buffers
Phosphates
X ray photoelectron spectroscopy
Earth (planet)
Ligands
Decomposition

ASJC Scopus subject areas

  • Catalysis

Cite this

Cobalt salophen complexes for light-driven water oxidation. / Asraf, Md Ali; Younus, Hussein A.; Ezugwu, Chizoba I.; Mehta, Akshay; Verpoort, Francis Walter Cornelius.

In: Catalysis Science and Technology, Vol. 6, No. 12, 2016, p. 4271-4282.

Research output: Contribution to journalArticle

Asraf, Md Ali ; Younus, Hussein A. ; Ezugwu, Chizoba I. ; Mehta, Akshay ; Verpoort, Francis Walter Cornelius. / Cobalt salophen complexes for light-driven water oxidation. In: Catalysis Science and Technology. 2016 ; Vol. 6, No. 12. pp. 4271-4282.
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